Intrinsic Factors chpt 5 Flashcards
Why is physical structure an intrinsic factor?
Idea that access to microbes reflects structure. (Parasites are an exception)
Why is nutrients and natural inhibitors an intrinsic factor?
Foods supply the nutrients for growth of the microorganism. Are the nutrients available to the microorganism tho?
Are the nutrients available to the microorganism? what do microorganisms have to help use nutrients?
Enzymes.
Starch requires amyloyltic enzymes.
Lactose requires B-galactosidases.
Yeast cannot use starch.
What is a chemoheterotroph?
organism that lives on food. doesn’t require specific requirements. like Pseudomonas spp. can grow in inorganic N and CO2.
What are a few natural inhibitors found in food?
Eggs have lysozyme in egg whites which hydrolyses peptidoglycan. After time lysozome is destroyed and bacteria can grow.
What is another example of a natural inhibitor?
HOPS found in beer which is a strong antimicrobial. Doesn’t destroy yeast though.
How is pH used as an intrinsic factor?
A lot of microorganisms cannot grow below a certain pH, therefore pH is lowered (very acidic) so microorganisms cannot grow.
What are the few microorganisms that aren’t really affected by pH?
LAB, yeat, mold, and fungi.
What is the min pH for Clostridium botululinum?
4.5
What is the min pH for most bacteria?
4.5
What is the min pH for Staphylococcus aureus?
4.0
pH for molds/ yeasts?
1.5- 3.5
What is water activity?
The ratio of the water vapor pressure in a food to the water vapor pressure of pure water.
Water activity for C. botulinum is?
9.0-9.8
How are most pathogenic bacteria grow inhibited by water activity?
with a water activity at 0.92
